The present invention relates to rubber mixtures containing carbon black, silica and rubber gels and are based on solution styrene/butadiene rubbers. The rubber mixtures of the present invention, in which a proportion of the silica or of the carbon black has been replaced by a rubber gel, have improved cushioning behavior at 0xc2x0 C. (resistance to slipping when wet) and improved rolling resistance (improved cushioning behavior at 60xc2x0 C.), without having other important mechanical properties, such as the resistance to wear of the vulcanizates produced from the rubber mixtures according to the invention, impaired. The processing behavior of the unvulcanized mixtures of the present invention remains virtually unimpaired, as shown by the relevant characteristics (compound viscosity and Mooney relaxation) of the mixtures. The rubber mixtures of the present invention can be used, in particular, to produce tire components of any type and to produce industrial rubber articles.
It is known to produce tires or tire components such as tire treads based on silica and carbon black-filled solution styrene/butadiene rubbers (L-SBR), polybutadiene rubbers (BR) and polyisoprene rubbers (IR and NR) with the proportion of the L-SBR greater than the proportion of other known rubbers. The vulcanizates produced from these mixtures are distinguished, in particular, by an advantageous combination of resistance to slipping when wet, rolling resistance and resistance to wear. Disadvantages when using these silica-filled rubber mixtures reside, in particular, in the high costs of specific components required, such as the filler activators and the high specific weight of the silica-filled mixtures associated with processing of the rubber mixtures, which is expensive in terms of energy due to the high viscosity and the high Mooney relaxation.
It is also known to use rubber and microgels as fillers in rubber mixtures. Reference is made, in particular, to EP-A-405 216, U.S. Pat. No. 5,395,891, U.S. Pat. No. 6,127,488 and DE-A 19 701 487. Although the use of an immense variety of rubber gels as fillers in various rubber mixtures is described in the aforementioned patent applications and patents, the aforementioned patent applications and patents do not teach that improved cushioning behavior at 0xc2x0 C. (resistance to slipping when wet) and improved rolling resistance (improved cushioning behavior at 60xc2x0 C.) associated with low wear without impairing the processing behavior of the unvulcanized rubber mixtures can be achieved by using small quantities of rubber gels in L-SBR rubber mixtures which contain silica and carbon black.
The present invention improves the aforementioned properties of rubber mixtures based on L-SBR together with good processing behavior of the unvulcanized rubber mixtures.
The present invention relates to rubber mixtures containing carbon black, silica and rubber gel which exhibit improved cushioning behavior at 0xc2x0 C. and improved rolling resistance without impairing the processing behavior of the unvulcanized rubber mixtures.
The rubber mixtures of the present invention contains
a) solution styrene/butadiene rubber (L-SBR)
b) silica
c) carbon black and
d) rubber gel,
wherein component a) is present in the mixture in a quantity of 100 parts by weight, component b) in a quantity of 20 to 120 parts by weight, component c) in a quantity of 5 to 60 parts by weight and component d) in a quantity of 0.1 to 10 parts by weight, providing that the proportion of component c) is 50 wt. % maximum based on the proportion of component b).